Drum Trap

I am completely remodeling a small 6'3"x6'7" bathroom. I plan to replace the shower with a neo-angle tiled shower using a Kerdi shower kit. Because I'm using the Kerdi system, I needed to replace the drain.

And so my troubles begin. As I break up the slab I find that the clamping drain is attached to what appears to be a 4" pipe going straight down. So I start digging. There must be a trap somewhere, right?

About 8" down I find the connection to the vent. It is at an upward angle and is cast into the "pipe". At about 12" down, I find the bottom of the pipe. Now I am on the hunt to find out where/how the water leaves this verticle pipe. I have dug most of the way around the pipe so it must be under vent pipe.

Well, I don't know whether it is good or bad news, but I do have a drum trap. A little more hammering and a little more research on how the trap works confirms it. I was very confused when I saw only one line coming out of the verticle 4" pipe and it appeared to line up with the vent line in the wall.

I can't figure out how to post a picture or I would. I believe I can cut the drain line, put a PVC line with P-trap in and I'll be back on track. I just have to verify my elevations so the drain doesn't end up going uphill.

Your description of a "vent" connected to the vertical line, and "only one line connected to the vertical pipe", is confusing because the line should have gone down, then turned horizontally to the trap with NO PIPES connected between the drain and the trap.

Here is a picture of what I am talking about. The line going up at a 45 deg angle is the only vent or drain line. The shower drain used to be on top of that 4" verticle pipe.

At first, I assumed the 45 deg. pipe was the vent line. More digging and more research showed that this was not a vent, but the drain line. The main drain header was just 2-3 inches below the finished level level of the shower drain. As water pored into that vertical pipe/trap, the water was forced up the 45 deg pipe and out the sewer. A good system, except when it fills up with hair and crud and clogs that outlet.

"I am not sure how they made that connection in such a short space, but if there is a trap below it, then that may be some handyman's idea of a way to connect a sink drain to the sewer system. "​

There is no trap below. This is the trap and it isn't a handyman special. It is a legitamate plumbing "fixture" from 40+ years ago. It works fine, except that it tends to collect gunk in the bottom that eventually fills up the trap to a level above the outlet. Then you have a problem, since there is no way to get a snake through it to clear it. Thus the invention of the P trap, I would guess. Another one of these I saw had a cleanout at the bottom. Good for a crawl space, bad for under slab.

It looks to be going into the vent but I would assume it ties into the 4" someplace. I would bet if you dig down a bit and rerun the lines like to the 4" like toolaholic said. This is because That copper is old and should be upgraded and now is the time to do it.

....is the only vent or drain line. ....
At first, I assumed the 45 deg. pipe was the vent line. More digging and more research showed that this was not a vent, but the drain line. The main drain header was just 2-3 inches below the finished level level of the shower drain. As water pored into that vertical pipe/trap, the water was forced up the 45 deg pipe and out the sewer. A good system, except when it fills up with hair and crud and clogs that outlet.

Click to expand...

true, that the weird thing you dug out of the ground was exactly as you described in this quoted paragraph. However, you had mixed up vent and drain beforehand, and the two previous posts had been confusing, so it still remains that things as you described them in general were self-contradictory until that point in time when you produced your second photo. It is not a drum trap. That pipe is not the vent.

As it stands now, I give you the highest respect for being able to figure out what things are and then to describe them in few words. Once you see them.

I guess you would have to call it something between a drum trap and a P trap. In 55+ years of plumbing I have never seen a trap like that so it may be something that was used regionally in some parts of the country.

Patrick88/toolhaholic - There is a sewer line in the wall were you can see the vent header. The drain line is connected to it.

Oh, and that line isn't copper - it's steel. If it was copper I would be cutting it all out, selling it and putting in pvc.

Plumbob - I just saw that episode of This Old House. A day late but interesting.

David - I'm a mechanical engineer, so I real good a designing plumbing on paper. Unfortunately, that doesn't mean I have had a lot of opportunities to to actually see the stuff I write on paper and I definately don't get to install it. Doing my own home repairs can be a bit humbling So I come here to learn.